Tetraplegia, also known as quadriplegia, is paralysis caused by illness or injury to a human that results in the partial or total loss of use of all their limbs and torso; paraplegia is similar but does not affect the arms. The loss is usually sensory and motor, which means that both sensation and control are lost. Tetraparesis or quadriparesis, on the other hand, means muscle weakness affecting all four limbs.[1] It may be flaccid or spastic.

Tetraplegia is caused by damage to the brain or the spinal cord at a high level C1–C7—in particular, spinal cord injuries secondary to an injury to the cervical spine. The injury, which is known as a lesion, causes victims to lose partial or total function of all four limbs, meaning the arms and the legs. Tetraplegia is defined in many ways; C1–C4 usually affects arm movement more so than a C5–C7 injury; however, all tetraplegics have or have had some kind of finger dysfunction. So, it is not uncommon to have a tetraplegic with fully functional arms but no nervous control of their fingers and thumbs.

It is possible to suffer a broken neck without becoming tetraplegic if the vertebrae are fractured or dislocated but the spinal cord is not damaged. Conversely, it is possible to injure the spinal cord without breaking the spine, for example when a ruptured disc or bone spur on the vertebra protrudes into the spinal column.

The condition of paralysis affecting four limbs is alternately termed tetraplegia or quadriplegia. Quadriplegia combines the Latin root quadra, for "four", with the Greek root πληγία plegia, for "paralysis". Tetraplegia uses the Greek root τετρα tetra for "four". Quadriplegia is the common term in North America; tetraplegia is more commonly used in Europe.[2]

Spinal cord injuries are classified as complete and incomplete by the American Spinal Injury Association (ASIA) classification. The ASIA scale grades patients based on their functional impairment as a result of the injury, grading a patient from A to D. (see table 1 for criteria) This has considerable consequences for surgical planning and therapy.[3]

Pathophysiologically, the spinal cord of the tetraplegic patient can be divided into three segments which can be useful for classifying the injury.

First there is an injured functional medullary segment. This segment has unparalysed, functional muscles; the action of these muscles is voluntary, not permanent and strength can be evaluated by the British Medical Research Council (BMRC) scale. This scale is used when upper limb surgery is planned, as referred to in the 'International Classification for hand surgery in tetraplegic patients' (see table 2).[4]

A lesional segment (or an injured metamere) consists of denervated corresponding muscles. The lower motor neuron (LMN) of these muscles is damaged. These muscles are hypotonic, atrophic and have no spontaneous contraction. The existence of joint contractures should be monitored.[4]

Below the level of the injured metamere there is an injured sublesional segment with intact lower motor neuron, which means that medullary reflexes are present, but the upper cortical control is lost. These muscles show some increase in tone when elongated and sometimes spasticity, the trophicity is good.[4]

The anterior cord syndrome: a lesion of the anterior horns and the anterolateral tracts, with a possible division of the anterior spinal artery.[5]

For most patients with ASIA A (complete) tetraplegia, ASIA B (incomplete) tetraplegia and ASIA C (incomplete) tetraplegia, the International Classification level of the patient can be established without great difficulty. The surgical procedures according to the International Classification level can be performed. In contrast, for patients with ASIA D (incomplete) tetraplegia it is difficult to assign an International Classification other than International Classification level X (others).[5] Therefore it is more difficult to decide which surgical procedures should be performed. A far more personalized approach is needed for these patients. Decisions must be based more on experience than on texts or journals.[5]

The results of tendon transfers for patients with complete injuries are predictable. On the other hand, it is well known that muscles lacking normal excitation perform unreliably after surgical tendon transfers. Despite the unpredictable aspect in incomplete lesions tendon transfers may be useful. The surgeon should be confident that the muscle to be transferred has enough power and is under good voluntary control. Pre-operative assessment is more difficult to assess in incomplete lesions.[5] Patients with an incomplete lesion also often need therapy or surgery before the procedure to restore function to correct the consequences of the injury. These consequences are hypertonicity/spasticity, contractures, painful hyperesthesias and paralyzed proximal upper limb muscles with distal muscle sparing.[5] Spasticity is a frequent consequence of incomplete injuries. Spasticity often decreases function, but sometimes a patient can control the spasticity in a way that it is useful to their function. The location and the effect of the spasticity should be analyzed carefully before treatment is planned. An injection of Botulinum toxin (Botox) into spastic muscles is a treatment to reduce spasticity. This can be used to prevent muscle shorting and early contractures.[5]

Over the last ten years an increase in traumatic incomplete lesions is seen, due to the better protection in traffic.

Although the most obvious symptom is impairment to the limbs, functioning is also impaired in the torso. This can mean a loss or impairment in controlling bowel and bladder, sexual function, digestion, breathing and other autonomic functions. Furthermore, sensation is usually impaired in affected areas. This can manifest as numbness, reduced sensation or burning neuropathic pain.[citation needed]

Severity depends on both the level at which the spinal cord is injured and the extent of the injury.

An individual with an injury at C1 (the highest cervical vertebra, at the base of the skull), will probably lose function from the neck down and be ventilator-dependent. An individual with a C7 injury may lose function from the chest down but still retain use of the arms and much of the hands.

The extent of the injury is also important. A complete severing of the spinal cord will result in complete loss of function from that vertebra down. A partial severing or even bruising of the spinal cord results in varying degrees of mixed function and paralysis. A common misconception with Tetraplegia is that the victim cannot move legs, arms or any of the major function; this is often not the case. Some tetraplegic individuals can walk and use their hands, as though they did not have a spinal cord injury, while others may use wheelchairs and they can still have function of their arms and mild finger movement, again, that varies on the spinal cord damage.

It is common to have movement in limbs, such as the ability to move the arms but not the hands or to be able to use the fingers but not to the same extent, as before the injury. Furthermore, the deficit in the limbs may not be the same on both sides of the body; either left or right side may be more affected, depending on the location of the lesion on the spinal cord.

There are about 5,000 cervical spinal cord injuries per year in the United States (~1 in 60,000—assuming a population of 300 million), and about 1,000 per year in the UK (also ~1 in 60,000—assuming a population of 60 million). In 1988, it was estimated that lifetime care of a 27-year-old rendered tetraplegic was about US $1 million and that the total national costs were US $5.6 billion per year.[citation needed] It currently costs between $520,000 to $550,000 per year to care for a ventilator dependent tetraplegic.[8]

Upper limb paralysis refers to the loss of function of the elbow and hand. When upper limb function is absent as a result of a spinal cord injury it is a major barrier to regain autonomy. There are possibilities for tetraplegic hand and elbow surgery which allow restoration of upper limb function. At the 2007 world congress[which?] in reconstructive hand surgery and rehabilitation in tetraplegia a resolution was presented and accepted that indicates that every person with tetraplegia should be examined and informed concerning the options for reconstructive surgery of the tetraplegic arms and hands. With this resolution it becomes clear that it is necessary to increase the awareness on this subject.[9] These surgical procedures are further discussed in upper-limb surgery in tetraplegia.

Delayed diagnosis of cervical spine injury has grave consequences for the victim. About one in 20 cervical fractures are missed and about two-thirds of these patients have further spinal-cord damage as a result. About 30% of cases of delayed diagnosis of cervical spine injury develop permanent neurological deficits. In high-level cervical injuries, total paralysis from the neck can result. High-level tetraplegics (C4 and higher) will likely need constant care and assistance in activities of daily living, such as getting dressed, eating and bowel and bladder care. Low-level tetraplegics (C5 to C7) can often live independently.[citation needed]

In the case of cerebral palsy, which is caused by damage to the motor cortex either before, during (10%), or after birth, some tetraplegics are gradually able to learn to stand or walk through physical therapy.